1. Field of the Invention
The present invention relates to a mounting structure in which an electronic component including a metal substrate, a semiconductor ceramic layer, and split electrodes, is mounted on a mounting body.
2. Description of the Related Art
Heretofore, as an NTC thermistor or a PTC thermistor, which is used as a temperature sensor in a protective circuit, a thermistor disclosed in Japanese Unexamined Patent Application Publication No. 61-245502 has been known. The thermistor disclosed in Japanese Unexamined Patent Application Publication No. 61-245502 is formed of a flat metal substrate also functioning as an electrode, a temperature-sensitive resistive film formed on one primary surface of the metal substrate, and one electrode film formed on the temperature-sensitive resistive film.
However, the above-described thermistor has a structure in which the flat metal substrate is used as one electrode, and the electrode film formed as the topmost layer is used as the other electrode. Hence, when this thermistor is mounted on a substrate or the like, an electrical connection to the electrode film has to be performed by wire bonding, and hence mounting to an extremely small space has been impossible. For example, when the thermistor as described above is used as a temperature sensor of an IC component mounted on a printed circuit board, a small space, such as 150 μm to 200 μm, is formed between the printed circuit board and the IC component, and the thermistor is preferably mounted in this space. However, it is practically difficult to perform mounting in this small space by wire bonding.
Accordingly, the invention disclosed in PCT/JP2010/64089 was developed by the present inventor. In particular, in the application disclosed PCT/JP2010/64089, there are provided a metal substrate, a thin thermistor layer formed on the metal substrate, and a pair of split electrodes formed on the thin thermistor layer. According to the structure as described above, solder mounting can be performed on a printed circuit board by a reflow method or the like. When solder mounting is performed, in general, in order to improve solder wettability, plating films are formed on the split electrodes. In the structure as described above, when a split-electrode side is mounted on lands formed on the printed circuit board, solder rise from the lands to a surface of the metal substrate occurs, and a problem that the split electrodes are electrically connected to the metal substrate with the solder occurs. As a result, a short-circuit defect is disadvantageously generated.